From 2b7b657f42880df9771cb82c75c19f16aa5d7952 Mon Sep 17 00:00:00 2001
From: yuanjize <1224500078@qq.com>
Date: Fri, 3 Jan 2020 19:41:09 +0800
Subject: [PATCH] ddl: throw warning when `ALTER TABLE ORDER BY` on table with
 primary key (#14324)

---
 ddl/db_test.go | 18 ++++++++++++++++++
 ddl/ddl_api.go | 13 +++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/ddl/db_test.go b/ddl/db_test.go
index 474090c0bd..44e254376c 100644
--- a/ddl/db_test.go
+++ b/ddl/db_test.go
@@ -4295,6 +4295,24 @@ func (s *testDBSuite2) TestDDLWithInvalidTableInfo(c *C) {
 	c.Assert(err.Error(), Equals, "[parser:1064]You have an error in your SQL syntax; check the manual that corresponds to your TiDB version for the right syntax to use line 1 column 94 near \"then (b / a) end));\" ")
 }
 
+func (s *testDBSuite1) TestAlterOrderBy(c *C) {
+	s.tk = testkit.NewTestKit(c, s.store)
+	s.tk.MustExec("use " + s.schemaName)
+	s.tk.MustExec("create table ob (pk int primary key, c int default 1, c1 int default 1, KEY cl(c1))")
+
+	// Test order by with primary key
+	s.tk.MustExec("alter table ob order by c")
+	c.Assert(s.tk.Se.GetSessionVars().StmtCtx.WarningCount(), Equals, uint16(1))
+	s.tk.MustQuery("show warnings").Check(testutil.RowsWithSep("|", "Warning|1105|ORDER BY ignored as there is a user-defined clustered index in the table 'ob'"))
+
+	// Test order by with no primary key
+	s.tk.MustExec("drop table if exists ob")
+	s.tk.MustExec("create table ob (c int default 1, c1 int default 1, KEY cl(c1))")
+	s.tk.MustExec("alter table ob order by c")
+	c.Assert(s.tk.Se.GetSessionVars().StmtCtx.WarningCount(), Equals, uint16(0))
+	s.tk.MustExec("drop table if exists ob")
+}
+
 func init() {
 	// Make sure it will only be executed once.
 	domain.SchemaOutOfDateRetryInterval = int64(50 * time.Millisecond)
diff --git a/ddl/ddl_api.go b/ddl/ddl_api.go
index c1c21599c9..644ba98ab2 100644
--- a/ddl/ddl_api.go
+++ b/ddl/ddl_api.go
@@ -2068,6 +2068,8 @@ func (d *ddl) AlterTable(ctx sessionctx.Context, ident ast.Ident, specs []*ast.A
 			}
 		case ast.AlterTableSetTiFlashReplica:
 			err = d.AlterTableSetTiFlashReplica(ctx, ident, spec.TiFlashReplica)
+		case ast.AlterTableOrderByColumns:
+			err = d.OrderByColumns(ctx, ident)
 		default:
 			// Nothing to do now.
 		}
@@ -4201,3 +4203,14 @@ func (d *ddl) RepairTable(ctx sessionctx.Context, table *ast.TableName, createSt
 	err = d.callHookOnChanged(err)
 	return errors.Trace(err)
 }
+
+func (d *ddl) OrderByColumns(ctx sessionctx.Context, ident ast.Ident) error {
+	_, tb, err := d.getSchemaAndTableByIdent(ctx, ident)
+	if err != nil {
+		return errors.Trace(err)
+	}
+	if tb.Meta().GetPkColInfo() != nil {
+		ctx.GetSessionVars().StmtCtx.AppendWarning(errors.Errorf("ORDER BY ignored as there is a user-defined clustered index in the table '%s'", ident.Name))
+	}
+	return nil
+}